Multiple TCP Clients
This application uses the ZentriOS TCP client command to open 4 simultaneous TCP connections to a TCP echo server on the internet (ZentriOS actually supports up to 8 simultaneous connections).
The TCP echo server, located on the internet at
test.zentri.com:50007, simply echoes all received data back to the ZentriOS TCP client.
Once each connection is established, stream_write is used to send data to each connection stream in turn.
With all data sent, stream_poll is used to check for received data on connection streams, and stream_read is used to read data waiting on a stream.
You will only need one Zentri evaluation board for this example.
Let's get started by connecting your board to a Wi-Fi network and opening each of the 4 TCP connection streams in turn. You can simply cut and paste the commands in the following table, but DON'T FORGET to replace your Wi-Fi network name and password for the defaults.
There is no need to bring up the WLAN network interface prior to opening a TCP connection, the TCP client (just like all commands that need the network) automatically connects to the network if a connection has not already been established.
An example showing what the session looks like if you entered the above commands successfully is shown below. Notice that each new TCP connection is assigned a stream handle, starting at 0 for the first TCP connection.
|Session log when opening 4 TCP client connections
Check the status of open streams before continuing. Use the stream_list command to get a list of open streams. The number in brackets appended to each line is the local port used for the TCP connection stream.
!# Type Info
#0 TCPC test.zentri.com:50007 (41713)
#1 TCPC test.zentri.com:50007 (46714)
#2 TCPC test.zentri.com:50007 (51715)
#3 TCPC test.zentri.com:50007 (56716)
Writing data to a stream is easy using the stream_write command. Copy and paste the following commands to write data to each open stream.
Checking for Data
To check for data on any stream (or all streams at once), use the stream_poll command as shown in the following session. If you don't want to poll for data, try assigning a GPIO to a stream to indicate when data is available. The tcp_client command describes how to assign a GPIO.
|Checking for data
To read available data from any stream, use the stream_read command as shown in the following session.
|Checking for data